Type-II collagen induced arthritis in mice (CIA) is a well studied animal model of inflammatory polyarthritis with many similarities to human rheumatoid arthritis (RA). In this model arthritis is induced in susceptible strains of mice and rats after immunization with hetrologous or autologous type-II collagen in complete Freund's adjuvant and the induction of arthritis is MHC restricted. In previous studies performed by our laboratory we identified a new CIA susceptible strain, BUB/BnJ (H-2q, TCR Vba), and showed that induction of arthritis in BUB mice is associated with a restricted use T cell antigen receptor (TCR) variable region genes (Vbeta) in the arthritic joints and was limited to TCR Vbeta3 and Vbeta10 genes. Most recently we demonstrated that mice preimmunized either with a mixture of TCR Vbeta3 and Vbeta10 peptides or with TCR Vbeta10 peptide alone were highly protected against the induction of CIA upon subsequent challenge with chicken type-II collagen (C-II) in CFA. The experiments in this proposal focus on further characterizing and understanding the mechanism of this protective immune response. The fundamental hypothesis of this proposal is that protective immunization induces an anti-Vbeta10 peptide immune response characterized by IFN-gamma producing T cells and IgG2a subtype antibodies (Th1 immune response) and this immune response subsequently results in the elimination or downregulation of the arthritogenic immune response. In order to perform these studies we have developed a highly sensitive ELISA spot assay capable of detecting cytokine production by single T cells, and have used this assay to show that (1) we can preferentially induce either a Th1 type or Th2 type anti-Vbeta10 immunity in vivo by simply altering the immunization protocol; (2) arthritis protected mice had anti-Vbeta10 specific CD4+ T cells which produced IFN-gamma while arthritic mice had IL-4 producing T cells. We will now fully characterize the recall Th1 or Th2 immune responses after immunization with Vbeta10P using the ELISA spot assay, standard cytokine ELISA and RT-PCR for cytokine message and TCR Vbeta gene usage. We will then determine how the induced anti-Vbeta10 immune response affects the quantity and cytokine profile of pathogenic immunity directed towards type-II collagen and towards a newly identified immunodominant determinant in BUB mice derived from type- collagen. Finally we will study how passive transfer of Vbeta10 specific antibodies and T cells affects the clinical expression of CIA as well as how it affects the pathogenic immune response directed at type-II collagen. The results obtained are expected to provide novel insight into the mechanisms of induced protective immune responses that may be relevant to the treatment of human rehumatoid arthritis and other autoimmune disorders.